Straddle-type vehicles, such as motorcycles, all-terrain vehicles (ATVs), personal watercraft, and three-wheeled road vehicles, are usually steered by a handlebar. Referring to FIG. 1, an exemplary prior art handlebar 10 is mounted to a vehicle (not shown) by clamping a clamp bar 14 portion of the handlebar 10 to a steering column 12 of the vehicle. The handlebar 10 is positioned forwardly of a straddle seat of the vehicle, and has left and right hand grips 16 on which the driver places his hands to steer the vehicle. The hand grips 16 are oriented generally transversely to the direction of travel of the vehicle, and may be angled rearwardly and either upwardly or downwardly to ensure that the hand grips 16 can be comfortably gripped by a typical driver, for example a 50th percentile adult male. The position of the hand grips 16 relative to the seat may be adjusted by pivoting the handlebar 10 about a horizontal clamp bar axis 18 coaxial with the clamp bar 14, to accommodate riders of different heights or arm lengths, or in different riding positions.
This type of handlebar has a number of drawbacks. While the position of the handlebar 10 is adjustable about the clamp bar axis 18, adjusting the position in this manner varies the position of the hand grips 16 both vertically and forwardly/rearwardly at the same time. Therefore, it offers only one degree of freedom for drivers who may wish to adjust more than one parameter independently, and the lateral separation of the hand grips is not adjustable at all. In addition, pivoting the handlebar 10 about the clamp bar axis 18 changes the orientation of the hand grips 16, which may result in poor ergonomics which are uncomfortable for the driver, particularly on longer trips.
This drawback is exacerbated when vehicle controls for controlling an operation of the vehicle, such as a throttle actuator, a brake lever, and/or various switches and buttons, are provided on the handlebar. These controls are typically situated within reach of a driver so that the driver can conveniently reach and actuate them while maintaining a grip on the hand grips to control the vehicle. Pivoting the handlebar 10 about the clamp bar axis 16 may significantly change the orientation of the controls, making them inconvenient or even inoperable for some drivers at some angles.
One attempt to address these problems is to provide additional degrees of freedom in adjusting the handlebar, such as an adjustable height riser supporting the handlebar on the steering column. However, an adjustable height riser does not completely address all of the drawbacks described above, and it is believed that further ergonomic improvements are possible.
In addition, providing additional degrees of freedom is generally at odds with the need for a structurally rigid steering assembly to withstand the stresses that are exerted while using the vehicle, particularly in racing and other high-structural stress applications. In general, a single piece or solidly welded handlebar is preferred when maximum structural rigidity is desired.
Therefore, there is a need for an adjustable steering assembly having more than one degree of freedom of adjustment.